1. Field of the invention
This invention relates to a molding of a foamed resin such as foamed polyurethane resin or the like, and a method for producing such moldings, which are particularly useful as head rests, arm rests, sunvisors, crash pads, bumpers of motor vehicles.
2. Description of the Prior Art
Moldings of a foamed resin such as foamed polyurethane resin are generally used as arm rests, crash pads and bumpers of motor vehicles, and the outer surfaces of the foamed resin moldings are generally covered with cloth or coated with a paint which gives a better appearance.
As a method for producing such molding, it is the usual practice to charge a foamable resin material into a mold which is applied with a parting agent on the inner surfaces thereof. In this connection, it is also known to overlay a film-like cover member on the mold cavity walls before charging a foamable resin to obtain a molding with a cover member integrally bonded to the surfaces of the molded body. Further, in the production of crash pads, an insert of a hard material is generally placed on one mold surface before molding for the purpose of shape retention or securing attachment to a vehicle body.
On the other hand, when molding a foamable resin, a parting agent of a fluorine-, wax- or silicontype is usually applied on the cavity walls for protection of the mold and at the same time for ensuring release of the molding. As a result, mold maintenance including periodical washing of the mold is required to remove the parting agent which would otherwise accumulate in the mold.
In addition, the parting agent which remains on the surfaces of the molding deteriorates the wettability with paint, inviting repellation of paint or irregularities in coating. Even in a case where a molding is free of these drawbacks, exudation of the parting agent on the coated surfaces often takes place with time, impairing the appearance and tactile impression of the products.
When piling the surfaces of a molding, in most cases there arise similar problems such as low wettability and repellation of adhesive, causing irregularities in thickness of the the coating. In such a case, the pile fibers are bonded defectively in those portions where the adhesive is repelled. On the contrary, in those portions where the adhesive is applied in a greater thickness, the adhesive tends to exude on the surface by capillary action along the bonded pile fibers, further adhering pile fibers there in a greater thickness than in other portion.
Therefore, the conventional process includes a washing step for removing the parting agent prior to the paint coating or adhesive applying stage. Nevertheless, it is regarded as almost impossible to eliminate the above-mentioned problems due to the difficulty of removing the parting agent completely from a molding of complicated shape.
There has been another problem that a parting line which is formed on a molding by the split portion of the mold becomes conspicuous after paint coating or piling in such a degree as to be detrimental to the appearance of the product.
There are also known molding methods without using a parting agent, for example, a method of charging a resin after overlaying a film-like cover member on mold cavity walls, a method of coating fluororesin or other releasing agent on cavity walls, and a method of plating mold cavity walls with chromium. However, in the case of the method of overlaying a film-like cover member on mold surfaces, a difficulty is encountered in laying film along cavity walls of complicated shape, taking time for this job. In case of the method of plating or coating a releasing material on mold cavity walls, the effect does not last long in spite of the high operational cost, failing to completely eliminate the use of a parting agent.
Heretofore, head rests and sunvisors are produced by molding a foamed resin body with cushioning property from a foamable, resin-like foamable urethane and then covering the foamed resin body in a bag-like cover member of cloth or the like. The bag-like cover member is generally formed into a shape complementary to the shape of the foamed resin body by sewing and fitted on the latter by heat-softening the cover member with steam in a case where the foamed resin body is of a simple shape. When the foamed resin body is of a complicated shape, however, it has been difficult to fit the bag-like cover member on the foamed resin body once and for all, necessitating to divide the cover member into a number of segments and to patch the respective segments after fitting on the foamed resin body.
Thus, the above-mentioned conventional method involves a large number of steps for fitting the bag-like cover member. Since the bag-like cover member is produced separately from the foamed resin body, dimensional errors in the manufacturing process often lead to the problem of wrinkling or slackening of the cover member after fitting same on the foamed resin body, which impairs the appearance of the final product.
In order to solve these problems, there has been made an attempt to foam and mold a foamable resin within a bag-like cover member. However, this method has problems such as leakage of the resin through the openings between the stitches in seamed portions of the cover member and impregnation and solidification of the resin into the stitches stiffening the seamed portions. Therefore, the fabrication of the bag-like cover member requires additional steps for stopping the openings in the seam stitches or forming seams by double sewing. In a case where the bag-like cover member is made of woven cloth or the like, there is a problem that the resin is likely to exude through the openings in the woven fabric itself.
Further, the inserts in the conventional foamed resin moldings are simply held in contact with the foamed resin of the moldings. Namely, since an insert which has low adhesion to the foamed resin body is easily detached from the foamed resin body, it has been necessary to select an insert from limited kinds of materials which show high adhesion to the foamed resin. In some cases, an adhesive is used for making up for the inferior adhesion to the foamed resin body, but this is disadvantageous in view of the increase in the number of steps and in the raw material cost.